The object of the present invention is to eliminate the difficulties of previous devices and to create an instrumented bearing which is particularly compact and reliable, and which also allows precise determination of the absolute angular position.
The instrumented bearing according to the present invention, which can be used especially for an electric steering wheel of a conveyor fitted with an electric direction control system, comprises an external element and an internal element whereof one is mobile in rotation about an axis relative to the other which is fixed, by means of at least a row of rolling elements disposed between said elements. The device also comprises means of detection of rotation parameters of the revolving element which comprise a sensor sensitive to magnetism arranged on a fixed part and a permanent magnet arranged on a revolving part, opposite the sensor, with its polar parts on either side of the axis of rotation.
The permanent magnet is mounted on a front face of the revolving element, on the side opposite the steering wheel.
In this way, absolute coding of the angular displacement of the revolving part is attained very simply and thus economically.
In a preferred embodiment, the sensor sensitive to magnetism comprises a plurality of cells of Hall effect distributed around a point corresponding to the axis of rotation of the revolving part equipped with the permanent magnet.
The sensor sensitive to magnetism can be advantageously created in the form of an integrated circuit chip and may comprise a plurality of contact pins enabling an electric current supply, where the output of the signal and programming of a predetermined angular position from the fixed part define a zero reference angle.
In another embodiment, the sensor sensitive to magnetism comprises a magnetoresistor centred on the axis of rotation.
The sensor sensitive to magnetism is preferably fixed on a printed circuit board mounted fixed in rotation in a space defined between the bearing and a closing cover which can have a connector. In this way, the support means of the steering wheel and the ensemble of electric processing means of the signal are integrated in the form of a unit. Once this unit is fixed on a vehicle or a machine, it suffices to mount the steering wheel and to connect an electric cable on the connector to make the ensemble function.
The electronic means for processing the signals and the electronic pilot means are preferably disposed oh the printed circuit board which already houses the sensor sensitive to magnetism. In this case, a simple change of printed circuit easily allows the device to be adapted to another application.
The link between the connector borne by the cover and the printed circuit board is preferably done by contact means, thus avoiding any connection cable.
Preferably, the sensor supplies a signal of absolute angular position relative to a zero reference position.
In a preferred embodiment, the permanent magnet is mounted in a recess on the revolving element so as not to project outside said front face. The axial bulkiness of the device is thus reduced to the maximum.
In a variant, the permanent magnet can be supported by a piece solid with a rotating ring of the bearing or even can be supported directly by the rotating ring of the bearing.
In an advantageous embodiment, the revolving part bearing the permanent magnet and a part at least of the steering wheel, indeed all the steering wheel, form a single monobloc piece. Assembly is accordingly particularly simple.
In a variant, the rotating ring of the bearing directly supports the steering wheel.
The permanent magnet can be a bipolar magnetised rod or a cylindrical element whose poles are situated on either side of the axis of rotation of the revolving part.